The present disclosure relates to fuel compositions, and more particularly to corrosion inhibitors for fuel compositions.
When combusted in a turbine, various inorganic contaminants in a fuel can affect turbine operation, particularly over extended periods of time. Certain contaminants in the fuel (e.g., sodium-, potassium-, lead-, mercury-, and vanadium-containing compositions) can cause corrosion of the various parts of the turbine. Although several corrosion mechanisms can occur, one frequently observed manifestation is the surface oxidation and/or pitting of the various turbine parts caused by low melting point (i.e., having a melting point lower than the operating temperatures to which they are exposed) ash deposits originating from these contaminants in the fuel. One approach to mitigate this so-called “hot corrosion” is to add a corrosion inhibitor to the fuel.
Corrosion inhibitors generally function by reacting with a specific contaminant to produce a more benign species, such as a higher melting point non-corrosive ash deposit. Unfortunately, over extended periods of operation, these and other deposits can build up and partially block the flow of cooling air as well as the hot gas through the turbine. Once a threshold level of blockage has been attained, the deposits must be removed by a cleaning procedure, which in some instances necessitates the shut down of the turbine.
There is a need for improved corrosion inhibitors, especially since the increased demand for energy has resulted in a greater number of situations where alternative sources of fuel or fuel with already higher than desired concentrations of contaminants are used. With these so-called “low-grade” fuels, an increase in the dosage of the corrosion inhibitors, while serving to reduce the potential for hot corrosion, will also result in increased build up of deposits and thus more frequent shut down of the turbine for cleaning. Therefore, it would be particularly advantageous if these improved corrosion inhibitors were more efficient than existing corrosion inhibitors.